There is an increasing desire to have ceramic products have antimicrobial protection. For example, there is the desire for both household and commercial purposes for such ceramic products to be free of germs and bacteria.
Although consumers want such ceramic products to have this functional feature, consumers also do not want to sacrifice the appearance of such ceramic products. This includes the appearance of sanitary ware. Sanitary ware typically requires higher firing temperatures and a longer time period.
Sanitary ware requires a significant increase in the amount of zinc to give it the desired aesthetic color and appearance. Bismuth and zinc are two of the most difficult antimicrobial components to put into a glaze. Bismuth particles melt at a lower temperature than zinc, and zinc may not go into solution with the other components of the glaze. At the firing temperatures (about 2250° F.) and length of firing time (18-24 hours) for sanitary ware, both the bismuth and the zinc can cause problems with increased fluidity and dripping of the glaze. In not blended well, both can cause discolorations. Bismuth produces clear spots in a white glaze, and zinc produces whiter areas. There is also dimpling. Zinc can also react with chrome and tin to alter the resulting glaze color.
Thus, there is a need for a method and an additive formulation to overcome these problems yet while providing an energy efficient solution.